a) Field of the Invention
The present invention is directed to a belt tensioning device for a belt conveyor, to be arranged in the area of the drive at the lateral edge of the conveyor belt.
b) Description of the Related Art
A wide variety of drive and power transmission arrangements for belt conveyors are known from prior art. DE 42 44 170 C2, for example, shows a driven frictional wheel that acts on the conveyor belt through frictional engagement. AT 355 983 shows a gearwheel drive with gears that engage in toothed strips on the underside of the conveyor belt; the power transmission is accordingly realized by way of a positive engagement.
Irrespective of the type of power transmission between drive and conveyor belt, there arises precisely in the area of the drive at the lateral edge of the conveyor belt the problem of a disturbance of power transmission caused by the conveyor belt xe2x80x9cslipping awayxe2x80x9d when the conveyor belt is loaded with goods to be conveyed. This kind of change in position of the conveyor belt negatively affects the power transmission and the running of the conveyor belt in general.
Therefore, it is the primary object of the invention to provide a belt tensioning device that ensures a constant position of the conveyor beltxe2x80x94even when the latter is loadedxe2x80x94in the area of the drive or of power transmission along the lateral edge of the belt.
In accordance with the invention, the belt tensioning device for a belt conveyor that is to be located in the area of the drive at the lateral edge of the conveyor belt has a guiding component part matching the edge area of the circulating conveyor belt and a contacting component part for direct contact with the surface of the conveyor belt; this contacting component part being located inside the guiding component part.
It has been recognized that securing the conveyor belt in position at the point of power transmission can be achieved when an additional structural component part is provided that acts upon the surface of the belt. Further, it has been recognized that for a low-loss holding down of the conveyor belt the component part advantageously has a structural form made up of two principal component parts. Finally, it has been recognized that a separation of the functions can be achieved by providing a guiding component part and a contacting component part. The guiding component part is used as a connection to the frame of the belt conveyor and to hold and guide the contacting component part. The contacting component part on the other hand realizes the positional securing of the conveyor belt through direct contact.
In order that the belt tensioning device according to the invention can be used on a belt conveyor, the guiding component part could be arranged at the end of a carrying drive pulley of the belt conveyor and fixed its side cheek. Also, instead of fixing it to the side cheek, a side component part of greater thickness could be used especially in the area of the drive. With regard to the construction of the belt tensioning device that includes the journal of the carrying drive pulley that is connected with the gear unit and motor, the side component part could extend on both sides of the journal. The side component part could preferably be bent at an angle and frame the belt tensioning device in such a way that it does not impede the running of the conveyor belt.
The embodiment example, described hereinafter, of the belt tensioning device according to the invention is directed to a type of power transmission that takes place between the carrying run and the return run of the conveyor belt. In particular, this is a gearwheel drive with one gear ring on the end of the carrying drive pulley and a toothed belt provided at the edge area of the conveyor belt in accordance with the German Patent Application 198 54 327.1 which does not form part of prior art. However, it should be noted at this point that the following embodiment example can be applied to any type of power transmission taking place between the carrying run and the return run of the conveyor belt.
Considering the preceding statements, the guiding component part could be designed essentially as a rectangular hollow body having an opening to receive or grip around the carrying drive pulley of the belt conveyor. The opening could advantageously extend in the area of a first main side and the rear side of the rectangular hollow body. The portion of the opening on the main side could be adapted to the cross-sectional dimensioning of the carrying drive pulley and can have be arc-shaped. Correspondingly, the rear-side portion of the opening could also be adapted to the maximum cross-sectional dimensioning of the carrying drive pulley, including the thickness of the conveyor belt. This results in a guiding component part that grips around the carrying drive pulley. The area of power transmission of the carrying drive pulley and the conveyor belt is more or less located in the arc-shaped recess.
As an alternative to a possible symmetric belt tensioning device that can be slipped onto the carrying drive pulley from the front, it is especially advantageous when the second main side of the guiding component part located opposite to the first main side with the above-described opening is formed so as to be almost completely closed and only has a through-opening for the journal of the carrying drive pulley. A substantially closed main side results on the one hand in a compact structural shape that is appropriate to the idea of guiding with regard to the contacting component part; on the other hand, the extensively closed main side gives more options for fixing the belt tensioning device according to the invention to the side cheek or a special side component part of the belt conveyor.
For fixing the device to the side cheek or to the side component part, various bore holes into which fastening means are inserted could be provided in the mostly closed main face. The rectangular block-shaped hollow body of the guiding component part could have a top side, a front side and a bottom side, in addition to the two main sides and the rear side. Further, with respect to the arc-like arrangement of the contacting component part, a sloping portion could be provided between the front side and the bottom side and between the front side and the top side, respectively. Also with respect to the supporting and shaping of the contacting component part, the front side could have a slit-shaped recess into which the contacting component part partially projects. When installed on the belt conveyor, the slit-shaped recess could be covered by the angled area of the side component part so as to achieve protection from and for the moveable contacting component part.
A further measure with respect to the bearing of the guiding component part is formed by a groove running inside the guiding component part. The extent of the groove inside the guiding component part couldxe2x80x94like the opening in the first main sidexe2x80x94be adapted to the cross-sectional dimensioning of the carrying drive pulley and follow an arc-like course. The groove could be essentially U-shaped in cross section. According to the present embodiment example, the groove could extend to the rear side of the guiding component part so that the free ends of the groove are open to the outside. But it would also be possible to provide a groove only in the area in which the contacting component part extends.
In a further embodiment form of the present embodiment example of the belt tensioning device according to the invention, the groove passes into the above-described slit-shaped construction of the front side and basically extends on both sides of the slit-shaped recess. In this manner, the groove in the area of the slit-shaped recess is defined only by the lateral edge areas, whereas there is no corresponding base.
With respect to an easy installation and manufacture of the belt tensioning device, the guiding component part could be made up of two parts, with the first and second part connected to each other in a detachable fashion in the manner of a lid and receptacle. One side boundary of the groove could advantageously be formed by the first part of the guiding component part and the base and other side boundary of the groove could be formed by the second part of the guiding component part. This has the advantage that the assembly of the guiding component part together with the contacting component part can be realized very simply and manufacture of the individual parts is simplified.
The contacting component part could have at least one means of contact in the shape of a ball bearing, a roller or a wheel to act upon the conveyor belt. Mobility of the bearing of the contacting means is essential so that there is no wear from excessive friction at the conveyor belt.
The bearing of the contacting component part could be realized by an axle arranged transverse to the course of the groove. To achieve a multiple and therefore more effective action upon the largest possible areas of the conveyor belt, it is advantageous to provide a plurality of axles, each with contacting means, which are arranged successively at a distance from each other. Depending on the load put on the conveyor belt and the type and design of power transmission means, it would also be possible to design the axles to receive a plurality of contacting means.
According to an especially preferable arrangement of the present embodiment example of the belt tensioning device according to the invention, a springing pressure piece could be provided; this would make it possible for the contacting means to be supported not only rotatably but also in a springing manner. This further reduces frictional wear of the surface of the conveyor belt, so that the contact between the contacting component part and conveyor belt is largely without consequences for the surface of the conveyor belt. Two springing pressure pieces forming the springing bearing for the axle on both sides of the centrally located contacting means are especially preferable.
In case a plurality of contacting means are to be used, these could be placed in the groove of the guiding component part and could protrude beyond the side limit of the groove; here again there is an adapting to the cross-sectional dimensioning of the carrying drive pulley, including the thickness of the belt. The embodiment form under discussion in which a plurality of contacting means is provided could have a total of eight contacting means, for example, in the form of ball bearings, each located on one axle. As regards the springing pressure pieces, only six pairs are required in the embodiment form under discussion. The six pairs of springing pressure pieces could be distributed in the area of the top side and bottom side as well as in the area of the sloping portions of the guiding component part, while two of the contacting means project into the slit-shaped recess of the front side. A springing bearing for the contacting means projecting into the slit-shaped recess of the front side is not strictly necessary insofar as the forces caused by the load of the goods to be conveyed are not as considerable at this location and the requirement for flexible means for securing in position is accordingly also not as demanding.
To permit easy readjustment of the springing pressure pieces, they could be accessible from the outside and, for example, readjusted via hexagon bolts.
The belt tensioning device according to the invention proceeds from a further development of the as yet unpublished German Patent Application 198 54 327.1 which is directed to a belt conveyor with a gearwheel drive between the carrying run and the return run, but it can also be applied to other types of power transmission, especially those between the carrying run and the return run. For the belt conveyor according to the German Patent Application 198 54 327.1, the problem to avoid was the disengaging of the teeth of the gearwheel of the carrying drive pulley and toothed belts on the bottom side of the belt when starting a loaded belt. The preceding embodiment form refers to this in particular; the belt tensioning device reaches over the outside surface of the conveyor belt in the area where the toothed belt is located and meshes with the gearwheel of the carrying drive pulley.
The teaching of the present invention can be advantageously configured and further developed in a variety of ways. In connection with the description of the above-mentioned embodiment example of the invention described below, preferred arrangements and further developments of the teaching are also described in general.